Take a look at this website:
https://illuminarepublications.com/scores/ordinary-time/

It has antiphons in English. For most weekdays in Ordinary Time, it's easiest to use the antiphons from the previous Sunday. There are also modern notation versions, which might be easy for you to start right away with.

The Lumen Christi Missal also has chant antiphons for the weekday Responsorial Psalms.

Hi and welcome to the forum, I was like you a while ago, a bit at sea with all this stuff and believe me there is all the help you need here and on the cmaa website. don't be afraid to ask.

Okay, here goes.
There are three chants for each mass - entrance or introit, offertory , and communion.
They all follow the same format - an antiphon, which is a bit like the chorus of a hymn, its is the bit you repeat, and in between you sing psalm verses, as you would the verses of a hymn. So each chant has the same format antiphon, psalm verse, repeat antiphon, another psalm verse, and so on, for as long or as short as you need. A short entrance procession for example, in our tiny parish church only ever needed the antiphon and one psalm verse. The longest one will probably be the communion, depending on how many are attending mass.
One word of caution - the antiphons printed in the missal are not the antiphons for singing - they are only for saying at masses where there is no singing. That is why there is no offertory antiphon printed, because the priest is saying the offertory prayer at this time. so for the purposes of a sung Mass you can ignore the antiphons in the missal, they are for spoken masses only. (there is an odd optional exception to this only for the american church, but it won't matter if you ignore that and do what the rest of the church does)

So now you know what you are looking for - three antiphons.

Where to find them?

Okay the go to book for the proper antiphons is the graduale romanum.
Which you can download for free here.
graduale romanum
but the easier place to go is thi handy website which does it all for you
a website that gets the proper antiphons for you
when you go to tht website, you make a few choices, and hey presto, it will give you a nice pdf of the music for your mass.
Here are the settings you will need to use
First - unless it is a special feast day or saints day, the amtiphons for a weekday are the same as the previous sunday.
Select the 'novus ordo' if you are doing the ordinary form mass (you probably are uless your priest has told you differently)
Select the previous sunday - for example last week it was the 30th sunday in ordinary time, and we are in year B.
Select which pieces you want in your pdf - you will want introitus, offertorium and communion.
you have the choice of full propers (the antiphons set to their proper music) or psalm tone antiphons,( a simpler way to sing the antiphons, but not the first choice to go for)

And there you have it - you now have some beautiful latin music to sing for mass.

but wait you say - what can the kids actually do with this stuff?

Okay, so now you know where the end point of your musical journey is, how do you get there?

Like any good teacher, you break it down into easier steps.

first you can reduce the new learning by singing the same antiphon for several weeks, by choosing one from the season. Just now we are in ordinary time, so you could for example use last sundays for more than one week. we are about to go into advent, you could do just one set from the four weeks of advent.

Second, start with something easier! Basically you can sing the same words to a simpler tune, and you can sing in english in stead of latin.

in terms of steps down to easier and easier -
Graduale romanum =Latin, full tune
Graduale simplex = latin, easier tune
Graduale parvum, = choice of latin or english, simplified melodies from the graduale romanum
Simple english propers = english, simplified melody line, quite easy for kids to learn
Psalm tone propers = english or latin, the right words sung to a psalm tone, very very simple, but gets boring , so not one to stay with long term.

all of the above can be found on or from the cmaa website for free,

And now the cool teaching part
Teachng music skills to your kids is an essential part of the long term plan. You will want them eventually to be able to take a piece of music and sing it through, so that practice is simple and about making it meautiful , not just teaching them the music line by line be ear.
In my experience it takes about one school year to teach a 6 year old how to read chant sufficient to be able to sing through something from the simple english propers by sight singing. They could sing a psalm tone proper from scratch in about 8 weeks. The go to method, developed specifically for teaching children to read and sing chant is the ward method, which could be part of another discussion? But again there are all sorts for free resources online for using it.

So if you wanted a recommendation for a plan:
Season 1 (the rest of ordinary time)
Sing psalm tone propers in english, as many as you can, but using the same one more than once if needed.

Season 2 Advent.
Go to the simple english propers - learn one set, do it all four weeks.

Season 3 Christmas / after christmas ordinary time
More simple english propers, with one communion proper from the graduale parvum in one ullenglish.

Season 4 lent
Simple english popers for entrance , another communion antiphon from the parvum, alternate with the one you already know, and learn one offertory from the graduale romanum.

Season 5 after easter
one full antiphon from graduale for entrance, simple english proers offertory, communio from parvum as before.

and so on to the next school year.
A you build up over time, each time you come back to a season, you find that you have some music in hand tht the older kids are familiar with from previous years. Als you investment in music reading skills is starting to pay off, so that they can tackle more complex pieces more quickly.

Full prpers for eacj distinct week of the year might be a stratch, but you certainly could get close to it over a number of years.

Something else to think about - if you are sing the propers (antiphons) then you should also be sing the ordinary (he response parts of the mass) and the priest should be singing his parts too. These will need time to work on, again, there are simpler sets and more complex sets, you can sing in english first, then latin to the same tune and so on.

DON'T PANIC. They are only school kids, how hard can that be? ;-)

sorry for all the typos. hope you got something from it.

That's excellent, bonniebede. Someone ought to give this post its own category over there on the right side of the forum.

A lot of this music is free online, and if you learn it yourself first, you can quite easily and quickly teach it, even in your short practice sessions.

simplify everything. though others here might be horrified, i have found that taize chants, especially the rounds and canons are useful stopgaps. You need only teach a simple two or three line melody, but when sung in parts it can sound quite sophisticated. This might help get over that initial learning period when you want to invest in new music and skills, but have to continue meeting expectations of great sounding music.

Ultimately this is a judgement call, which all the stakeholders must understand.
You can take a class of 8 yr olds, teach them something complex by rote, drill them in it for a long time, and have them perform it very well. It will sound great, the mummys will be thrilled - BUT - their actual skill set will have increased only very marginally.
Alternatively you can invest more heavily in skills, using simpler music, repeated more frequently, but by the end of the year they will have made real progress.

This is only a problem for the first year or two. By the end of your second year, your more seniors will have outstripped the ones who learn by rote. Their repertoire will be growing much faster, and their skill set for sight reading and singing will be immeasurably better.

Part of the choice comes down to whether you see your role as producing a performance or of educating the children. They are not the same goal, and sometimes can be in conflict.

You are in a wonderful predicament. Relish it, but yes, you have a lot of work ahead.

I would take some time to explain to Father that learning music -- especially a new style of music -- takes time. It is important for non-musicians to appreciate this fact.

Having said that, many things can change immediately and then be improved over time. For example, sitting down at an organ is no more difficult than sitting down at a piano. You won't really be 'playing organ' so much as 'playing piano on the organ', but you'll be giving Father an immediate change, and perhaps then you can reassure him that in the medium and long term, you plan on further improvements.

Of course, there is a line, somewhere, between an acceptable change to something that is better than what you have now but nowhere near ideal, in contrast to an unacceptable change to something that could be better, but right now is much worse. As others suggested, if you keep everything very simple at first, you should be able to remain safely on the right side of that line.

Can i also add that you are very blessed, many would give their eyeteeth for this opportunity!

Thank you so much everyone for your input, I don't feel so overwhelmed now. I think I am understanding what I need to do.... for now anyway. I am looking at The Simple English Propers online and they seem fairly simple to start with. I am confused about the Introits end with "Glory be..." Is that something I need to do? I saw Gloria Patri somewhere, but I don't know what that is. Forgive my ignorance.

This is a wonderful opportunity, MusicStar - and we're all praying for your success in this endeavor!

I would most definitely take advantage of specific generous people here - Bonniebede and Kevin come to mind - who can support you with more interactive conversations. The problem with the forum is that: (1) you can get a variety of answers to a question, some helpful, some diverging; (2) it's hard to ask a question in which you confess your own ignorance (congratulations on your courage starting this thread!); and (3) you'll have a zillion questions, and it can feel to you like you're spraying them all over this forum.

So take advantage of this forum, certainly, but if you can get someone to volunteer to mentor you between now and Christmas, it'll help you to move forward swiftly and keep your spirits up. It may just be a half hour Skype call every week, it doesn't have to be a huge imposition on you or on them.

Keep up your courage and focus, and it'll be wonderful! This is entirely doable!

CGZ, I suspect that when the priest recommended looking at "Musica Sacra", he didn't mean the 1958 document about music for the (old) Mass. He probably meant our (CMAA) websites, including this forum.